Progressive suspension device for the rear wheel of a motorcycle

ABSTRACT

The invention relates to a progressive suspension device ( 1 ) for the rear wheel of a motorcycle, comprising a swinging fork ( 2 ) that has a central section ( 10 ) to which one or two arms ( 8, 9 ) carrying a wheel ( 7 ) are connected. The suspension device further comprises a spring-damper assembly ( 14 ) connected at one end to a support ( 13 ) for the central section ( 10 ) of the fork ( 2 ), a rocker or lever ( 15 ) having a first end ( 16 ), with axis ( 16   a ), pivoted in seats ( 17 ) made in the engine crankcase ( 12 ) or in the motorcycle frame, the lever ( 15 ) also having a second end ( 18 ), with axis ( 18   a ), connected to the spring-damper assembly ( 14 ), a connecting rod ( 19 ) of length (C) joining the fork ( 2 ) to the lever ( 15 ). The connecting rod ( 19 ) comprises a first end ( 20 ) pivoted at an intermediate mounting point ( 21 ) between the first end ( 16 ) and the second ( 18 ) of the lever ( 15 ), and a second end ( 22 ) pivoted in a seat ( 23 ) made in the central section ( 10 ) of the fork ( 2 ). At the lever ( 15 ), between the mounting point ( 21 ) where the connecting rod ( 19 ) is pivoted and the axis ( 18   a ) of the second end ( 18 ), there is an angle (α) that may be varied to adapt the suspension device ( 1 ) to different progressive suspension needs.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a progressive suspension devicefor the rear wheel of a motorcycle. The progressive, rear-wheelsuspension device according to the present invention comprises aswinging fork for a wheel acting on a single damping spring assemblythrough at least one connecting rod and one rocker.

[0002] Rear-wheel suspension devices of this type are known, forexample, from U.S. Pat. No. 4,076,271.

[0003] The U.S. patent describes a vehicle wheel suspension device forthe rear wheel of a motorcycle. In one embodiment of it, this prior artsuspension device comprises a fork for a rear wheel and two rodsconnected at the end of the fork close to the wheel in such a way as totransfer the force applied by the wheel on the fork to a single springand damper through an intermediate swing element. The rods transmit onlyaxial type forces and are arranged in such a way as to form the edges ofa pyramid with downward pointing apex. In another embodiment of theinvention, the fork has a reticulate structure whose elements aresubjected mainly to normal forces.

[0004] Although the suspension device of the patent just describeddiscloses solutions, such as the single spring and dampers, which makeit possible to reduce overall dimensions, it is difficult to constructbecause it is based on unsubstantial components which, if they are to besubjected to only axial forces, must be constructed with extremely highdimensional and assembly precision. Further, the suspension device isdifficult to adjust in terms of the ratio of force to wheel movement andis also unsuitable for a suspension device consisting of a fork with asingle swing arm.

[0005] The present invention has for one of its objects to provide animproved progressive suspension device for the rear wheel of amotorcycle that may be applied to forks with either one or two arms,that may be easily adjusted in terms of the ratio of force to wheelmovement, and that is easy to adapt to the constructional tolerances ofthe motorcycle to which it has to be fitted.

[0006] Another object of the present invention is to provide arear-wheel suspension device that is economical, compact and occupiesparts of the motorcycle that are not normally used.

SUMMARY OF THE INVENTION

[0007] In accordance with one aspect of it, the present inventiondiscloses a progressive suspension device for the rear wheel of amotorcycle as described in the independent claim below. The dependentclaims describe preferred, advantageous embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The preferred embodiments of the invention will now be described,without restricting the scope of the inventive concept, with referenceto the accompanying drawings in which:

[0009]FIG. 1 is a side view of the progressive rear-wheel suspensiondevice according to the present invention;

[0010]FIG. 2 is a view from below, with some parts cut away and othersin cross section, of the progressive rear-wheel suspension device shownin FIG. 1;

[0011]FIG. 3 is a schematic side view of the progressive rear-wheelsuspension device illustrated in the figures listed above; and

[0012] FIGS. 4 to 6 are diagrams relating to the progressive rear-wheelsuspension device illustrated in the figures listed above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] With reference to the accompanying drawings, the numeral 1denotes a progressive suspension device for the rear wheel of amotorcycle.

[0014] The suspension device 1 comprises a swinging fork 2 having afirst end 3 pivoted at a pin 4 and a second end 5 that carries an axle 6of a wheel 7.

[0015] The swinging fork 2 may comprise one or two arms 8, 9 connectedat a central section 10.

[0016] Preferably, the pin 4 of the fork 2 is rotatably fitted insideseats 11 made in the engine crankcase 12, although the pin 4 may also befitted in similar seats 11 in the motorcycle frame without therebydeparting from the scope of the inventive concept of the presentinvention.

[0017] The central section 10 of the swinging fork 2 presents a support13 for mounting a spring-damper assembly 14.

[0018] The suspension device 1 comprises a rocker or lever 15 pivoted ata first end 16, with axis 16 a, in seats 17 made in the engine crankcase12 or in the motorcycle frame.

[0019] The lever 15 presents a second end 18, with axis 18 a, connectedto the spring-damper assembly 14.

[0020] The suspension device 1 further comprises a connecting rod 19joining the fork 2 to the lever 15.

[0021] The connecting rod 19 comprises a first end 20 pivoted at anintermediate mounting point 21 between the first end 16 and the secondend 18 of the lever 15, and a second end 22 pivoted in a seat 23 made inthe central section 10 of the fork 2. The connecting rod 19 is dividedinto two parts to enable the spring-damper assembly 14 to pass throughthe connecting rod 19 and, at its second end 22, comprises means 24 foradjusting the length C of the connecting rod 19 itself. The means 24 mayconsist of a lead nut and screw mechanism with a lock nut 24 a, butother devices might also be used: for example, a rod with a seriestransversal holes in it and a pin that can be selectively inserted intoone of the holes.

[0022] An important geometrical parameter of the suspension device 1 isthe angle of the lever 15, labeled a in FIGS. 1 and 3.

[0023] This angle is made by the line passing through the axes 16 a and18 a of the ends 16, 18 of the lever 15 with the line passing throughthe axis 16 a and the axis of the mounting point 21 at which theconnecting rod 19 is pivoted.

[0024] As shown in the examples below, variations in the angle α of thelever 15, and hence in the length C of the connecting rod 19—and to alesser extent also in the other parameters—have a marked effect on theoperating progression of the suspension.

[0025] The angle α of the lever 15 may have values ranging from −20 to80 degrees. With negative angle values, a highly compact structure canbe obtained, with, in particular, a connecting rod 19 of reduced length.

[0026] Preferably, as a compromise between compactness and stress on thecomponents, the angle a ranges from 20 to 70 degrees.

[0027] The operation of the suspension device will now be described.

[0028] When the wheel 7 is displaced relative to the motorcycle engineor frame, the fork 2 swings about its pin 4 and thus causes a mainlyaxial movement of the connecting rod 19.

[0029] The latter, which is in turn connected to the lever 15 at thepivoted mounting point 21, causes the lever 15 to rotate about the axis16 a.

[0030] This has the effect of pushing the second end 18 of the lever 15in such a way that it describes an arc F and causes the lower end of thespring-damper assembly 14 to also move.

[0031] The other end of the spring-damper assembly 14 is mounted in sucha way that it can swing slightly on the support 13 of the fork 2. Thanksto this structure, the spring-damper assembly 14 is compressed orreleased according to the movements of the wheel 7 in a progressive orlinear fashion. The performance of the structure can be significantlychanged just by slightly modifying the geometrical characteristics ofthe lever 15 and adjusting the length C of the connecting rod 19accordingly.

[0032] Different embodiments of the suspension device 1 will now bedescribed with reference to the following examples and with the aid ofthe schematic representation of it in FIG. 3.

[0033] Considering a virtual origin O, the dimensions X and Y define theposition of the fork 2 pin 4 and the position of the axis 16 a of thelever 15.

[0034] Other important geometrical elements defined in FIG. 3 are:

[0035] the angle α of the lever 15, defined above;

[0036] the fork-connecting rod angle, labeled β, made by the linepassing through the axis of the pin 4 and the axle 6 of the wheel 7 withthe line passing through axis of the pin 4 and the axis of theconnecting rod 19 seat 23; depending on the required dimensions andprogressive suspension needs, the angle β ranges from 0 to 40 degrees;

[0037] the fork-damper angle, labeled γ, made by the line passingthrough the axis of the pin 4 and the axle 6 of the wheel 7 with theline passing through axis of the pin 4 and the axis of the pivot pointof the spring-damper assembly 14; depending on the required dimensionsand progressive suspension needs, the angle γ ranges from 0 to 70degrees;

[0038] the length of the fork 2, labeled L, defined as the distancebetween the axis of the pin 4 and the axle 6 of the wheel 7;

[0039] the fork-connecting rod length, labeled A, defined as thedistance between the axis of the pin 4 and the axis of the connectingrod 19 seat 23;

[0040] the length of the connecting rod 19, labeled C, defined as thedistance between the axes of pivot points of the connecting rod 19 ends20 and 22;

[0041] the fork pin-damper pivot point length, labeled G, defined as thedistance between the axis of the pin 4 and the axis of the pivot pointof the spring-damper assembly 14;

[0042] the lengths of the lever 15, labeled E and H, defined,respectively, as the distance between the axis 16 a of the lever 15 andthe axis of the mounting point 21 at which the connecting rod 19 ispivoted, and the distance between the axes 16 a and 18 a of the lever15.

[0043] FIGS. 4 to 6 show three diagrams relating to three differentembodiments. The x-axis represents the stroke in millimeters of the axle6 of the wheel 7. The y-axis on the left represents the non-dimensionalvalue of the ratio of the variation in the stroke of the axle 6 of thewheel 7 to the variation in the stroke of the spring-damper assembly 14.The y-axis on the right represents the load in Newton (N) axle 6 of thewheel 7. The curves labeled CR represent the load on the axle 6 of thewheel 7, while the curves labeled LR represent the ratio of thevariation in the wheel stroke to the variation in the stroke of theassembly 14. This ratio is also known as lever ratio.

[0044] The characteristics of the spring-damper assembly 14, the same inall the embodiments, are the following: maximum length mm 305.0 elasticconstant of spring N/mm 104 preload mm 9 gas pressure bar 12.0 gas forceN 246 total stroke mm 74.0 free stroke mm 60.0

[0045] The geometrical characteristics of the suspension device 1 in theembodiment represented by FIG. 4 are shown in the table below: L [mm]550.0 β [degrees] 20.00 A [mm] 180.00 γ [degrees] 50.0 G [mm] 100.0 X[mm] −70.000 Y [mm] −150.000 C [mm] 269.0 E [mm] 60.0 H [mm] 150.0 α[degrees] 70.0

[0046] The results for the suspension device 1 in the embodimentrepresented by FIG. 4 are shown in the table below: Lever- Wheel Ass.yratio Relative axle 6 14 non- Ass.y Wheel 7 wheel 7 Progression strokestroke dimen- 14 load load load non- [mm] [mm] sional [N] [N] [N/mm]dimensional 0.0 0.0 1.51 1200 797 46.7 0.0% 10.0 6.6 1.54 1895 1229 44.6−2.4% 20.0 13.0 1.58 2576 1635 42.7 −4.6% 30.0 19.3 1.61 3242 2017 41.0−6.7% 40.0 25.4 1.64 3895 2380 39.6 −8.7% 50.0 31.5 1.66 4538 2726 38.3−10.5% 60.0 37.4 1.69 5169 3057 37.1 −12.3% 70.0 43.3 1.72 5791 337436.0 −14.0% 80.0 49.1 1.74 6405 3678 35.0 −15.6% 90.0 54.8 1.76 70093971 34.0 −17.2% 100.0 60.4 1.79 7606 4254 33.2 −18.7% 110.0 66.0 1.818195 4527 32.3 −20.2% 120.0 71.5 1.83 8777 4790 31.6 −21.7% 130.0 76.91.85 9352 5044 30.8 −23.1%

[0047] It will be noticed in this embodiment that increasing the wheelaxle stroke reduces the load needed to move the wheel (relative wheelload). This feature is also evidenced in the <<Progression>> column,where all the values are negative, indicating this reduction inpercentage terms.

[0048] In the second embodiment, the modified geometricalcharacteristics of the suspension device 1 are α=20.0 degrees andC=221.1 mm.

[0049] The results for the suspension device 1 in the embodimentrepresented by FIG. 5 are shown in the table below: Lever- Wheel Ass.yratio Relative axle 6 14 non- Ass.y Wheel 7 wheel 7 Progression strokestroke dimen- 14 load load load non- [mm] [mm] sional [N] [N] [N/mm]dimensional 0.0 0.0 2.07 1200 578 24.6 0.0% 10.0 4.9 2.04 1710 841 25.51.7% 20.0 9.8 2.01 2239 1117 26.4 3.3% 30.0 14.8 1.97 2772 1407 27.35.0% 40.0 20.0 1.93 3315 1715 28.3 6.8% 50.0 25.2 1.90 3869 2040 29.58.6% 60.0 30.5 1.86 4433 2386 30.7 10.4% 70.0 35.9 1.82 5010 2755 32.112.3% 80.0 41.5 1.78 5599 3150 33.6 14.3% 90.0 47.2 1.73 6203 3576 35.216.4% 100.0 53.0 1.69 6822 4037 37.1 18.5% 110.0 59.0 1.64 7458 453939.3 20.8% 120.0 65.2 1.59 8113 5091 41.7 23.2% 130.0 71.6 1.54 87895702 44.6 25.7%

[0050] In this embodiment, increasing the wheel axle stroke increasesthe load needed to move the wheel (relative wheel load). This feature isalso evidenced in the <<Progression>> column, where all the values arepositive, indicating this increase in percentage terms. It should alsobe noticed that these values show a more marked increase for the lastpart of the wheel stroke.

[0051] In the third embodiment, the modified geometrical characteristicsof the suspension device 1 are α=46.1 degrees and C=247.9 mm.

[0052] Lastly, the results for the suspension device 1 in the embodimentrepresented by FIG. 6 are shown in the table below: Lever- Wheel Ass.yratio Relative axle 6 14 non- Ass.y Wheel 7 wheel 7 Progression strokestroke dimen- 14 load load load non- [mm] [mm] sional [N] [N] [N/mm]dimensional 0.0 0.0 1.92 1200 624 28.6 0.0% 10.0 5.2 1.93 1750 908 28.5−0.2% 20.0 10.4 1.93 2300 1192 28.5 −0.3% 30.0 15.6 1.93 2849 1475 28.4−0.4% 40.0 20.7 1.93 3398 1758 28.4 −0.5% 50.0 25.9 1.93 3946 2042 28.4−0.5% 60.0 31.1 1.93 4495 2326 28.4 −0.4% 70.0 36.3 1.93 5043 2611 28.4−0.4% 80.0 41.4 1.93 5592 2898 28.5 −0.3% 90.0 46.6 1.93 6142 3187 28.5−0.2% 100.0 51.8 1.92 6693 3479 28.6 0.0% 110.0 57.0 1.92 7244 3773 28.80.2% 120.0 62.2 1.92 7797 4071 28.9 0.4% 130.0 67.5 1.91 8351 4372 29.00.7%

[0053] In this last case, the force needed to move the wheel (relativewheel load) remains substantially constant and the load-movementcharacteristics of the suspension device vary in practically linearfashion. This feature is also evidenced in the <<Progression>> column,where all the values are around zero percent.

[0054] As demonstrated in the embodiments described above, thesuspension device 1 according to this invention can be easily adapted tosuit a wide variety of progressive suspension needs. By making minorconstructional changes to the geometry of the lever 15, it is possibleto obtain large variations in the operation of the suspension device.

[0055] Since all the geometrical changes required are concentrated inthe lever 15 and, to a lesser extent, in the connecting rod 19, it isvery easy to substitute these parts and to adapt them to differentsuspension needs.

[0056] Other important advantages of the progressive suspension devicefor the rear wheel of a motorcycle according to the present inventionare the following:

[0057] The entire suspension device 1 requires only two points ofconnection to the motorcycle frame or engine. In particular, thespring-damper assembly 14 is supported entirely by the suspension deviceitself and does not require reaction points on the frame or engine toabsorb stresses. This makes it very easy to mount and remove thesuspension device and to position it on the motorcycle frame.

[0058] More specifically, the suspension device 1 can be easily fittedand removed by simply using the two pins attaching the fork 2 and thelever 15. This facilitates maintenance because it means the entire rearsection of the motorcycle can be separated.

[0059] When the suspension device 1 is supported directly by the enginecrankcase, the motorcycle frame structure is further simplified since itdoes not require the mounting points for the suspension device.Suspension driving precision is also greatly enhanced because themounting points directly on the engine are much more rigid.

[0060] The suspension device 1 is extremely compact and occupies a partof the motorcycle that is normally not used.

[0061] The suspension device 1 according to the present invention can beapplied to swinging forks with either one or two arms. In any case, theforces applied by the spring-damper assembly 14 are absorbed by thecentral section 10 of the swinging fork, thus allowing greater freedomin the configuration of the fork arms.

[0062] The heaviest parts of the suspension device 1 (the spring-damperassembly 14 and the connecting rod) are located at the bottom, thuslowering the center of gravity of the motorcycle. Also, they are closeto the suspension's center of oscillation (the axis of the pin 4), thusreducing the inertia with which the suspension device 1 follows thebumps and hollows on the road the motorcycle is traveling on.

[0063] The invention as described above may be modified and adapted inseveral ways without thereby departing from the scope of the inventiveconcept as defined in the claims.

[0064] List of Reference Characters

[0065]1 suspension device

[0066]2 swing fork

[0067]3 first end of fork 2

[0068]4 pin of fork 2

[0069]5 second end of fork 2

[0070]6 wheel axle

[0071]7 wheel

[0072]8 first arm of swing fork 2

[0073]9 second arm of fork 2

[0074]10 central section of fork 2

[0075]11 seats for pin 4

[0076]12 engine crankcase

[0077]13 support for spring-damper assembly

[0078]14 spring-damper assembly

[0079]15 lever

[0080]16 first end of lever 15

[0081]16 a axis of first end of lever 15

[0082]17 seats for first end 16

[0083]18 second end of lever 15

[0084]18 a axis of second end of lever 15

[0085]19 connecting rod

[0086]20 first end of connecting rod 19

[0087]21 intermediate pivoted mounting point of lever 15

[0088]22 second end of connecting rod 19

[0089]23 seats for second end 22 of connecting rod 19

[0090]24 adjustment means

[0091]24 a lock nut

What is claimed is:
 1. A progressive suspension device (1) for the rearwheel of a motorcycle, comprising: a swinging fork (2) having a firstend (3) pivoted at a pin (4) fitted inside at least one seat (11) madein an element selected from the group consisting of engine crankcase(12) and motorcycle frame, and a second end (5) that carries an axle (6)of a wheel (7), the fork (2) having a central section (10), providedwith a seat (23) and to which there is connected at least one arm (8, 9)to support the wheel (7); a spring-damper assembly (14) connected at oneend to a support (13) for the central section (10) of the fork (2); alever (15) having a first end (16), provided with a pivoting axis (16a), the lever (15) being pivotable at the pivoting axis (16 a) in atleast one seat (17) made in an element selected from the groupconsisting of engine crankcase (12) and motorcycle frame, the lever (15)also having a second end (18), provided with a connecting axis (18 a),the lever (15) being associated at the connecting axis (18 a) to theother end of the spring-damper assembly (14); a connecting rod (19), oflength (C), joining the fork (2) to the lever (15), said connecting rod(19) having a first end (20) associated to the lever (15) at anintermediate point (21) between the first end (16) and the second end(18) of the lever (15), and a second end (22) associated to the seat(23) of the central section (10) of the fork (2).
 2. The suspensiondevice (1) according to claim 1, wherein the connecting rod (19) isdivided into two parts to enable the passage of the spring-damperassembly (14).
 3. The suspension device (1) according to claim 1,wherein the connecting rod (19) comprises means (24) for adjusting itslength (C).
 4. The suspension device (1) according to claim 1,comprising means (24) for adjusting the length (C) of the connecting rod(19), located at the second end (22) of the connecting rod (19).
 5. Aprogressive suspension device (1) for the rear wheel of a motorcycle,comprising: a swinging fork (2) having a first end (3) pivoted at a pin(4) fitted inside at least one seat (11) made in an element selectedfrom the group consisting of engine crankcase (12) and motorcycle frame,and a second end (5) that carries an axle (6) of a wheel (7), the fork(2) including a central section (10), provided with a seat (23) and towhich there is connected at least one arm (8, 9) to support the wheel(7); a spring-damper assembly (14) connected at one end to a support(13) for the central section (10) of the fork (2); a lever (15) having afirst end (16), provided with a pivoting axis (16 a), the lever (15)being pivotable at the pivoting axis (16 a) in at least one seat (17)made in an element selected from the group consisting of enginecrankcase (12) and motorcycle frame, the lever (15) also having a secondend (18), provided with a connecting axis (18 a), the lever (15) beingassociated at the connecting axis (18 a) to the other end of thespring-damper assembly (14); a connecting rod (19), of length (C),joining the fork (2) to the lever (15), said connecting rod (19) havinga first end (20) associated to the lever (15) at an intermediate point(21) between the first end (16) and the second end (18) of the lever(15), and a second end (22) associated to the seat (23) of the centralsection (10) of the fork (2); the second end (18) and the intermediatepoint (21) of the lever (15) being positioned according to an angle (α)made by the line passing through the axes (16 a, 18 a) of the ends (16,18), with the line passing through the axis (16 a) and the intermediatepoint (21) at which the connecting rod (19) is associated.
 6. Thesuspension device (1) according to claim 5, wherein the angle (α) rangesfrom 20 to 70 degrees.
 7. The suspension device (1) according to claim5, wherein the connecting rod (19) comprises means (24) for adjustingits length (C).
 8. The suspension device (1) according to claim 5,wherein the connecting rod (19) is divided into two parts to enable thespring-damper assembly (14) to pass through the connecting rod (19)itself.
 9. A progressive suspension device (1) for the rear wheel of amotorcycle, comprising: a swinging fork (2) having a first end (3)pivoted at a pin (4) fitted inside at least one seat (11) made in anelement selected from the group consisting of engine crankcase (12) andmotorcycle frame, and a second end (5) that carries an axle (6) of awheel (7), the fork (2) including a central section (10), provided witha seat (23) and to which there is connected at least one arm (8, 9) tosupport the wheel (7); a spring-damper assembly (14) connected at oneend to a support (13) for the central section (10) of the fork (2); alever (15) having a first end (16), provided with a pivoting axis (16a), the lever (15) being pivotable at the pivoting axis (16 a) in atleast one seat (17) made in an element selected from the groupconsisting of engine crankcase (12) and motorcycle frame, the lever (15)also having a second end (18), provided with a connecting axis (18 a),the lever (15) being associated at the connecting axis (18 a) to theother end of the spring-damper assembly (14); a connecting rod (19), oflength (C), joining the fork (2) to the lever (15), said connecting rod(19) having a first end (20) associated to the lever (15) at anintermediate point (21) between the first end (16) and the second end(18) of the lever (15), and a second end (22) associated to the seat(23) of the central section (10) of the fork (2); the axle (6) of thewheel (7) and the seat (23) for the connecting rod (19) on the lever(15) being positioned according to an angle (β) made by the line passingthrough the axis of the pin (4) and the axle (6) of the wheel (7) withthe line passing through the axis of the pin (4) and the axis of theseat (23) for the connecting rod (19).
 10. The suspension device (1)according to claim 9, wherein the angle (β) ranges from 0 to 40 degrees.11. The suspension device (1) according to claim 9, wherein theconnecting rod (19) comprises means (24) for adjusting its length (C).12. A progressive suspension device (1) for the rear wheel of amotorcycle, comprising: a swinging fork (2) having a first end (3)pivoted at a pin (4) fitted inside at least one seat (11) made in anelement selected from the group consisting of engine crankcase (12) andmotorcycle frame, and a second end (5) that carries an axle (6) of awheel (7), the fork (2) including a central section (10), provided witha seat (23) and to which there is connected at least one arm (8, 9) tosupport the wheel (7); a spring-damper assembly (14) connected at oneend to a support (13) for the central section (10) of the fork (2); alever (15) having a first end (16), provided with a pivoting axis (16a), the lever (15) being pivotable at the pivoting axis (16 a) in atleast one seat (17) made in an element selected from the groupconsisting of engine crankcase (12) and motorcycle frame, the lever (15)also having a second end (18), provided with a connecting axis (18 a),the lever (15) being associated at the connecting axis (18 a) to theother end of the spring-damper assembly (14); a connecting rod (19), oflength (C), joining the fork (2) to the lever (15), said connecting rod(19) having a first end (20) associated to the lever (15) at anintermediate point (21) between the first end (16) and the second end(18) of the lever (15), and a second end (22) associated to the seat(23) of the central section (10) of the fork (2); the axle (6) of thewheel (7) and the mounting point of the spring-damper assembly (14)being positioned according to an angle (γ) made by the line passingthrough the axis of the pin (4) and the axle (6) of the wheel (7) withthe line passing through the axis of the pin (4) and the axis of themounting point of the spring-damper assembly (14).
 13. The suspensiondevice (1) according to claim 12, wherein the angle (γ) ranges from 0 to70 degrees.
 14. A progressive suspension device (1) for the rear wheelof a motorcycle, comprising: a swinging fork (2) having a first end (3)pivoted at a pin (4) fitted inside at least one seat (11) made in anelement selected from the group consisting of engine crankcase (12) andmotorcycle frame, and a second end (5) that carries an axle (6) of awheel (7), the fork (2) including a central section (10), provided witha seat (23) and to which there is connected at least one arm (8, 9) tosupport the wheel (7); a spring-damper assembly (14) connected at oneend to a support (13) for the central section (10) of the fork (2); alever (15) having a first end (16), provided with a pivoting axis (16a), the lever (15) being pivotable at the pivoting axis (16 a) in atleast one seat (17) made in an element selected from the groupconsisting of engine crankcase (12) and motorcycle frame, the lever (15)also having a second end (18), provided with a connecting axis (18 a),the lever (15) being associated at the connecting axis (18 a) to theother end of the spring-damper assembly (14); a connecting rod (19), oflength (C), joining the fork (2) to the lever (15), said connecting rod(19) having a first end (20) associated to the lever (15) at anintermediate point (21) between the first end (16) and the second end(18) of the lever (15), and a second end (22) associated to the seat(23) of the central section (10) of the fork (2); the second end (18)and the pivoted mounting point (21) of the lever (15) being positionedaccording to an angle (α) made by the line passing through the axes (16a, 18 a) of the ends (16, 18), with the line passing through the axis(16 a) and the mounting point (21) at which the connecting rod (19) ispivoted; the axle (6) of the wheel (7) and the seat (23) for theconnecting rod (19) on the lever (15) being positioned according to anangle (β) made by the line passing through the axis of the pin (4) andthe axle (6) of the wheel (7) with the line passing through the axis ofthe pin (4) and the axis of the seat (23) for the connecting rod (19);the axle (6) of the wheel (7) and the mounting point of thespring-damper assembly (14) being positioned according to an angle (γ)made by the line passing through the axis of the pin (4) and the axle(6) of the wheel (7) with the line passing through the axis of the pin(4) and the axis of the mounting point of the spring-damper assembly(14).
 15. The suspension device (1) according to claim 14, wherein theangle (α) ranges from 20 to 70 degrees.
 16. The suspension device (1)according to claim 14, wherein the angle (β) ranges from 0 to 40degrees.
 17. The suspension device (1) according to claim 14, whereinthe angle (γ) ranges from 0 to 70 degrees.
 18. The suspension device (1)according to claim 14, wherein the connecting rod (19) is divided intotwo parts to enable the passage of the spring-damper assembly (14). 19.The suspension device (1) according to claim 14, wherein the connectingrod (19) comprises means (24) for adjusting its length (C).